Modern pipelined microprocessors use speculative execution to reduce the cost of conditional branch instructions. When a conditional branch instruction is encountered, the processor guesses which way the branch is most likely to go (this is called branch prediction), and immediately starts executing instructions from that point. If the guess later proves to be incorrect, all computation past the branch point is discarded. The early execution is relatively cheap because the pipeline stages involved would otherwise lie dormant until the next instruction was known. However, wasted instructions consume Central Processing Unit (CPU) cycles that could have otherwise delivered performance, and on a laptop, those cycles consume battery power.